Working Paper Article Version 6 This version is not peer-reviewed

Partial Unlock for COVID-19-Like Epidemics Can Save 1-3 Million Lives Worldwide

Version 1 : Received: 13 April 2020 / Approved: 15 April 2020 / Online: 15 April 2020 (10:02:51 CEST)
Version 2 : Received: 16 April 2020 / Approved: 17 April 2020 / Online: 17 April 2020 (08:48:55 CEST)
Version 3 : Received: 9 May 2020 / Approved: 10 May 2020 / Online: 10 May 2020 (15:14:11 CEST)
Version 4 : Received: 15 May 2020 / Approved: 16 May 2020 / Online: 16 May 2020 (16:13:16 CEST)
Version 5 : Received: 20 May 2020 / Approved: 21 May 2020 / Online: 21 May 2020 (04:13:13 CEST)
Version 6 : Received: 14 July 2020 / Approved: 15 July 2020 / Online: 15 July 2020 (03:14:33 CEST)

How to cite: Shuler, R.L.; Koukouvitis, T.; Suematsu, D. Partial Unlock for COVID-19-Like Epidemics Can Save 1-3 Million Lives Worldwide. Preprints 2020, 2020040239 Shuler, R.L.; Koukouvitis, T.; Suematsu, D. Partial Unlock for COVID-19-Like Epidemics Can Save 1-3 Million Lives Worldwide. Preprints 2020, 2020040239

Abstract

Background: A large percentage of deaths in an epidemic or pandemic can be due to overshoot of population (herd) immunity, either from the initial peak or from planned or unplanned exit from lockdown or social distancing conditions. Objectives: We study partial unlock or reopening interaction with seasonal effects in a managed epidemic to quantify overshoot effects on small and large unlock steps and discover robust strategies for reducing overshoot. Methods: We simulate partial unlock of social distancing for epidemics over a range of replication factor, immunity duration and seasonality factor for strategies targeting immunity thresholds using overshoot optimization. Results: Seasonality change must be taken into account as one of the steps in an easing sequence, and a two step unlock, including seasonal effects, minimizes overshoot and deaths. It may cause undershoot, which causes rebounds and assists survival of the pathogen. Conclusions: Partial easing levels, even low levels for economic relief while waiting on a vaccine, have population immunity thresholds based on the reduced replication rates and may experience overshoot as well. We further find a two step strategy remains highly sensitive to variations in case ratio, replication factor, seasonality and timing. We demonstrate a three or more step strategy is more robust, and conclude that the best possible approach minimizes deaths under a range of likely actual conditions which include public response.

Supplementary and Associated Material

http://shulerresearch.org/covid19.htm: model results frequently updated, latest model download

Subject Areas

epidemic; caseload management; partial unlock; social distancing; overshoot; COVID-19; coronavirus; economic impact; ventilator utilization; SARS-CoV-2

Comments (1)

Comment 1
Received: 15 July 2020
Commenter: Robert Shuler
Commenter's Conflict of Interests: Author
Comment: A new section 4 has been added discussing calibration of unlock levels in the two months since previous version, and whether overshoot is a problem currently, in the winter or in the post-vaccine era.
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